The working process of the ejector is as follows. The high-pressure (ejecting) gas at full pressure flows out of the nozzle into the mixing chamber. In the stationary mode of operation of the ejector, a static pressure is set in the inlet section of the mixing chamber which is always below the total pressure of the low-pressure (ejected) gas .

Under the influence of the pressure difference, low-pressure gas rushes into the chamber. The relative flow rate of this gas, called the ejection coefficient
, depends on the areas of the nozzles, on the density of gases and their initial pressures, and on the operating mode of the ejector. Despite the fact that the velocity of the ejected gas in the inlet section usually less than the ejector gas velocity , proper selection of nozzle areas And one can obtain an arbitrarily large value of the ejection coefficient n.

The ejecting and ejected gases enter the mixing chamber in the form of two separate flows: in the general case, they can differ in chemical composition, velocity, temperature, and pressure. The mixing of flows means, ultimately, the alignment of the parameters of the gases over the entire cross section of the chamber.

The whole mixing process can be conditionally divided into two stages - initial and main. Accordingly, two sections of the mixing chamber are distinguished (Fig. 5). The flow in the initial section of the mixing chamber, with a known approximation, can be likened to a turbulent jet moving in a cocurrent flow. Due to the presence of transverse fluctuating velocity components inherent in turbulent motion, the flows are introduced into each other, forming a gradually widening mixing zone - the boundary layer of the jet. Within the boundaries of the boundary layer, there is a smooth change in the parameters of the gas mixture from their values ​​in the ejecting gas to the values ​​in the ejected gas. Outside the boundary layer, in the initial section of the mixing chamber, there are undisturbed flows of the ejected and ejecting gases.

In the initial section of the chamber, the particles of the ejected gas are continuously captured by the high-pressure jet and entrained by it into the mixing zone. Due to this, a vacuum is maintained at the inlet to the mixing chamber, which ensures the inflow of low-pressure gas into the ejector.

Depending on the relative dimensions of the ejector, both zones of the unperturbed gas flow sequentially disappear with increasing distance from the nozzle; so, in fig. 5, the core of the ejecting jet is eliminated first.

At some distance from the nozzle, in the section G - G, called the boundary section, the boundary layer of the jet fills the entire section of the mixing chamber. There are no regions of undisturbed flows in this section, but the gas parameters are significantly different along the chamber radius. Therefore, even after the boundary section in the main section of the mixing chamber, the alignment of the flow parameters over the section continues. In the final section of the chamber, which is spaced on average at a distance of 8–12 chamber diameters from the initial section, a fairly homogeneous mixture of gases is obtained, the total pressure of which greater than the total pressure of the ejected gas , the lower the ejection coefficient n. Rational design of the ejector is reduced to the choice of its geometric dimensions so that, for given initial parameters and the ratio of gas flow rates, to obtain the highest value of the total pressure of the mixture, or at given initial and final pressures to obtain the largest ejection coefficient.

Rice. 5. Variation of the velocity field along the length of the mixing chamber.

The above-described scheme of the process of mixing gases in an ejector at subsonic velocities is fundamentally no different from the process of mixing incompressible liquids in a liquid ejector. As will be shown below, even at large subcritical pressure ratios, not only qualitative regularities, but also many quantitative dependences between the parameters of a gas ejector practically do not differ from the corresponding data of a liquid ejector.

A qualitatively new flow pattern is observed at supercritical pressure ratios in the nozzle. With a subsonic outflow, the gas pressure at the outlet of the nozzle is equal to the pressure in the environment, in other words, the static pressures of the gases at the inlet to the mixing chamber p 1 and p 2 are the same. In the case of sonic or supersonic outflow of the ejecting gas, the pressure at the nozzle exit can differ significantly from the pressure of the ejected gas.

If the nozzle of the ejecting gas is made non-expanding, then at a supercritical pressure ratio, the static pressure on the nozzle exit exceeds the pressure in the environment - the ejected gas.

Rice. 6. Scheme of the flow in the initial section of the mixing chamber at a supercritical pressure ratio in the nozzle

Therefore, after leaving nozzle A, the ejecting gas jet B (Fig. 6), moving at the speed of sound
, continues to expand, its speed becomes supersonic, and the cross-sectional area becomes larger than the area of ​​the outlet section of the nozzle.

A supersonic ejector jet flowing out of a Laval nozzle behaves in exactly the same way if a supersonic nozzle with incomplete expansion is used in the ejector. In this case, the gas velocity at the nozzle exit corresponds to
, Where
is the calculated value of the velocity for a given Laval nozzle, which is determined by the ratio of the areas of the outlet and critical sections.

Thus, at pressure ratios greater than those calculated for a given nozzle, the ejecting gas in the initial section of the mixing chamber is an expanding supersonic jet. The ejected gas flow in this section moves between the jet boundary and the chamber walls. Since the speed of the ejected flow in the initial section is subsonic, when flowing through a narrowing "channel", the flow accelerates, and the static pressure in it drops.

At the subsonic outflow of the ejecting jet, the greatest rarefaction and maximum flow velocities were achieved in the inlet section of the chamber. In this case, the minimum value of the static pressure and the maximum velocity of the ejected flow are achieved in a section of 1 ", located at a certain distance from the nozzle, where the area of ​​the expanding supersonic jet becomes the largest. This section is commonly called the blocking section.

A feature of the supersonic jet is that its mixing with the surrounding flow in this area is much less intense than the mixing of subsonic flows. This is due to the fact that the supersonic jet has an increased stability compared to the subsonic jet, and the blurring of the boundaries of such a jet is weaker. The physical basis of this phenomenon is easy to understand in the following example (Fig. 7).

Rice. Fig. 7. Scheme of the force effect of gas on a body that bends the boundary between subsonic (a) and supersonic (b) flows.

If the boundary of the subsonic flow is curved due to some reason (for example, the impact of co-flow gas particles), then in this place, due to a decrease in the cross-sectional area, the static pressure decreases and an external pressure force arises that increases the initial deformation of the boundary: when interacting with the environment the subsonic jet "draws in" the particles of the external flow and its boundary is rapidly blurred. In a supersonic (with respect to the external medium) flow, a similar curvature of the boundary and a decrease in the cross section lead to an increase in pressure; the emerging force is directed not inside, but outside the flow and tends to restore the initial position of the jet boundary, pushing out particles of the external environment.

It is interesting to note that this difference in the properties of subsonic and supersonic jets can be observed literally by touch. A subsonic jet draws in a light object brought to the boundary; a supersonic jet has a "hard" boundary at a distance of several calibers from the nozzle; when trying to introduce an object into the jet from the outside, a noticeable resistance is felt at the sharply pronounced boundary of the jet.

Rice. 8. Schlieren - photograph of the flow in the mixing chamber of a flat ejector in the subsonic mode of gas outflow from the nozzle;
,
, p 1 \u003d p 2.

Rice. 9. Schlieren - photograph of the flow in the mixing chamber of a flat ejector at a supercritical pressure ratio in the nozzle P 0 =3.4.

On fig. Figures 8 and 9 show photographs of the flow in the initial section of the mixing chamber for subsonic and supersonic outflow of the ejecting jet. The photographs were taken on a flat ejector model, the regime was changed by increasing the total pressure of the ejecting gas in front of the nozzle at a constant pressure of the ejected gas and a constant pressure at the outlet of the chamber.

The photographs show the difference between the two considered flow regimes in the initial section of the chamber.

When analyzing the processes and calculating the parameters of the ejector at supercritical pressure ratios in the nozzle, we assume that up to the blocking cross section (Fig. 6), the ejecting and ejected flows flow separately without mixing, and intensive mixing occurs behind this section. This is very close to the actual picture of the phenomenon. The blocking cross section is a characteristic cross section of the initial mixing section, and the flow parameters in it, as will be shown below, significantly affect the working process and the ejector parameters.

With distance from the nozzle, the boundary between the flows blurs, the supersonic core of the ejecting jet decreases, and the gas parameters gradually equalize over the chamber cross section.

The nature of the mixing of gases in the main section of the mixing chamber is practically the same as at subcritical pressure ratios in the nozzle, the velocity of the gas mixture in a wide range of initial gas parameters, the speed of sound remains lower. However, as the ratio of the initial gas pressures increases beyond a certain value determined for each ejector, the mixture flow in the main section of the chamber becomes supersonic and may remain supersonic until the end of the mixing chamber. The conditions for the transition from subsonic to supersonic gas mixture flow, as will be shown below, are closely related to the gas flow regime in the blocking section.

These are the features of the flow of the process of mixing gases at supercritical ratios of gas pressures in the ejecting nozzle. Note that by the pressure ratio in the nozzle we mean the ratio of the total pressure of the ejecting gas to the static pressure of the ejected flow in the inlet section of the mixing chamber , which depends on the total pressure and reduced speed .

The more , the greater (at a constant ratio of total gas pressures) the ratio of pressures in the nozzle:

Here
is a well-known gas dynamic function.

Thus, the supercritical regime of ejecting gas outflow from the nozzle can also exist when the ratio of the initial total gas pressures
below the critical value.

Regardless of the characteristics of the flow of gases during mixing, the velocity of the gases is equalized over the cross section of the chamber by the exchange of momentum between particles moving at a higher and lower speed. This process is accompanied by losses. In addition to the usual hydraulic losses due to friction against the walls of the nozzles and the mixing chamber, the working process of the ejector is characterized by losses associated with the very essence of the mixing process.

Let us determine the change in kinetic energy that occurs when two gas flows are mixed, the second mass flow rate and the initial velocity of which are, respectively, G 1 , G 2 , And . If we assume that the mixing of flows occurs at a constant pressure (this is possible either with a special profiling of the chamber or with mixing of free jets), then the amount of movement of the mixture should be equal to the sum of the initial amounts of movement of the flows:

The kinetic energy of a mixture of gases is

It is easy to verify that this value is less than the sum of the kinetic energies of the flows before mixing, which is equal to

by the amount

. (2)

Value
represents the loss of kinetic energy associated with the process of mixing flows. These losses are similar to the energy losses during the impact of inelastic bodies. Regardless of the temperature, density and other parameters of the flows, as formula (2) shows, the greater the greater the difference in the speeds of the mixing flows. From this we can conclude that for a given velocity of the ejecting gas and a given relative flow rate of the ejected gas
(ejection coefficient) to obtain the smallest losses, i.e., the highest value of the total pressure of the gas mixture, it is desirable to increase so as to bring the speed of the ejected gas as close as possible to the speed of the ejecting gas at the entrance to the mixing chamber. As will be seen below, this indeed leads to the most advantageous flow of the mixing process.

Rice. 10. Change of static pressure along the length of the mixing chamber at subsonic flow of gases.

When mixing gases in the cylindrical mixing chamber of the ejector, the static pressure of the gases does not remain constant. In order to determine the nature of the change in static pressure in a cylindrical mixing chamber, we compare the flow parameters in two arbitrary sections of the chamber 1 and 2, located at different distances from the beginning of the chamber (Fig. 10). Obviously, in section 2, which is located at a greater distance from the inlet section of the chamber, the velocity field is more uniform than in section 1. If we assume that for both sections
(for the main section of the chamber, where the static pressure changes insignificantly, this approximately corresponds to reality), then from the condition of equality of second gas flow rates

it follows that in sections 1 and 2 the average value of the flow velocity over the area remains constant

.(3)

. (4)

It is easy to verify that when
, i.e. in the case of a uniform velocity field in section F, the value is equal to one. In all other cases, the numerator in (4) is greater than the denominator and
.

The value of the quantity can serve as a characteristic of the degree of non-uniformity of the velocity field in a given section: the more non-uniform the field , the more . We will call the quantity field coefficient.

Returning to fig. 10, it is now easy to conclude that the value of the field coefficient in section 1 is greater than in section 2. The momentums in sections 1 and 2 are determined by the integrals

Because
, then it follows

(5)

So, the amount of motion in the flow when the velocity field is equalized during the mixing process decreases, despite the fact that the total flow rate and the average velocity over the area
remain constant.

Let us now write the momentum equation for the flow between sections 1 and 2:

.

Based on inequality (5), the left side of this equation is always positive. Hence it follows that
i.e., the alignment of the velocity field in the cylindrical mixing chamber is accompanied by an increase in static pressure; in the inlet section of the chamber there is a reduced pressure compared to the pressure at the outlet of the chamber. This property of the process is directly used in the simplest ejectors, consisting of a nozzle and one cylindrical mixing chamber, as, for example, shown in Fig. 10. Due to the presence of vacuum at the entrance to the chamber, this ejector sucks air from the atmosphere, and then the mixture is thrown back into the atmosphere. On fig. 10 also shows the change in static pressure along the length of the ejector chamber.

The resulting qualitative conclusion is valid in cases where the change in gas density in the considered section of the mixing process is insignificant, as a result of which we can approximately assume
. However, in some cases of mixing gases of significantly different temperatures, when there is a large density non-uniformity over the cross section, as well as at supersonic speeds in the main mixing section, when the density changes noticeably along the length of the chamber, ejector operation modes are possible in which the static pressure of the gas during mixing does not increases and decreases.

If the mixing chamber is not cylindrical, as assumed above, but has a cross-sectional area variable along the length, then an arbitrary change in the static pressure along the length can be obtained.

The main geometric parameter of the ejector with a cylindrical mixing chamber is the ratio of the areas of the outlet sections of the nozzles for the ejecting and ejected gases

,

where F 3 - cross-sectional area of ​​the cylindrical mixing chamber.

Big value ejector , i.e. with a relatively small chamber area, is high-pressure, but cannot work with large ejection coefficients; small ejector allows you to suck a large amount of gas, but little increases its pressure.

The second characteristic geometrical parameter of the ejector is the expansion degree of the diffuser
- the ratio of the cross-sectional area at the outlet of the diffuser to the area at the entrance to it. If the ejector operates at a given static pressure at the outlet of the diffuser, for example, when exhausting into the atmosphere or into a tank with a constant gas pressure, then the degree of expansion of the diffuser f significantly affects all the parameters of the ejector. With an increase in f, in this case, the static pressure in the mixing chamber decreases, the ejection rate and the ejection coefficient increase, with a slight change in the total pressure of the mixture. Of course, this is true only until the moment when the speed of sound is reached in any section of the ejector.

The third geometric parameter of the ejector is the relative length of the mixing chamber
- is not included in the usual methods for calculating the ejector, although it significantly affects the parameters of the ejector, determining the completeness of the alignment of the mixture parameters over the cross section. Below we will assume that the length of the chamber is sufficiently large
and field coefficient in its outlet cross section is close to unity.

Entrainment in higher pressure flow moving at high speed, low pressure media

Animation

Description

The effect of ejection is that a high-pressure flow moving at high speed drags a low-pressure medium with it. The entrained flow is called ejected. In the process of mixing the two media, the velocities are equalized, usually accompanied by an increase in pressure.

The main feature of the physical process is that the mixing of flows occurs at high speeds of the ejecting (active) flow.

Since coaxial jets do not propagate in a constant-pressure atmosphere, but are limited by channel walls or mixing chambers, the average axial momentum, averaged over the mass flow rate, is not kept constant, and the static pressure can vary along the x-axis. As long as the velocity of the ejecting flow is greater than the velocity of the ejected flow in a mixing chamber of constant radius, there will be an increase in pressure in the x direction, where the nuclei are absorbed due to the rapid mixing of the shear layers (the core is that part of the direct flow that enters the channel).

The process of mixing flows in the ejector chamber is schematically illustrated in fig. 1.

Mixing flows in the ejector chamber

Rice. 1

In the section 0 - 0 , coinciding with the beginning of the mixing chamber, the average speed of the working (ejecting) flow V E and suction (ejected) flow V EJ are initial. Behind this section is the initial section of the mixing of flows, where the core of the speed of the working flow is stored in the center, not covered by the mixing process. Within the core, the flow velocities are constant and equal to the average outflow velocity from the nozzle V E .

A similar core of constant velocities can be observed within the annular region covered by the intake flow. Between these areas of constant speeds there is a zone of turbulent exchange, where the flow rates are constantly changing from V E in the core of the working flow to V EJ in the suction flow zone. The initial section ends in the alignment, where the core of the working flow is wedged out.

When the wedge-out points of the working flow velocity core and the suction flow velocity core do not coincide, a transitional section appears between the initial and main sections, within which there is only one of the constant velocity zones.

The mixing of flows in the ejector chamber is accompanied by changes in the average pressure along the flow path. As the profile of the transverse distribution of flow velocities is leveled and the average velocity of the total flow decreases from section to section, the pressure increases.

The pressure increase in the mixing zone of a channel of constant radius without taking into account surface friction against the wall can be determined by the formula:

,

where p 0 - pressure in the section 0-0;

p 1 - pressure in section 1-1 (Fig. 1);

r is the density of the substance;

V E - speed of the working flow;

V A - suction flow rate;

And E is the ratio of the areas of the nozzle and the chamber (relative expansion).

The effect manifests itself, for example, in a cylindrical pipe in the presence of at least two jet streams with different velocities.

The material flow takes the form of a channel or a chamber in which the flows are mixed.

Timing

Initiation time (log to -1 to 1);

Lifetime (log tc 1 to 9);

Degradation time (log td from -1 to 1);

Optimal development time (log tk 1 to 6).

Diagram:

Technical realizations of the effect

Technical implementation of the ejection effect

For the technical implementation of the ejection effect, it is enough to direct the air flow from a home vacuum cleaner into the intake pipe of the system shown in Fig. 2.

The simplest ejection system

Rice. 2

The simplest ejection system is included in the package of Soviet household vacuum cleaners

1- tube with a stream of ejecting air;

2 - branch pipe for supplying the ejected liquid;

3 - tank with ejected liquid;

4 - air flow;

5 - spray cone of the ejected liquid.

Bernoulli rarefaction in the air stream draws liquid (aqueous colored solution) from the tank, and the air stream atomizes it by detaching drops from the end of the inlet pipe. The difference in height between the liquid level in the tank and the spray point (the end of the pipe) is 10 - 15 cm. The inner diameter of the tube with the gas flow is 30 - 40 mm, the inlet pipe is 2 - 3 mm.

Applying an effect

Increasing the pressure of the ejected flow without direct mechanical energy is used in jet devices that are used in various branches of technology: at power plants - in fuel combustion devices (gas injection burners); in the power supply system of steam boilers (anti-cavitation water jet pumps); to increase pressure from turbine extractions (steam jet compressors); for air suction from the condenser (steam jet and water jet ejectors); in air cooling systems of generators; in heating installations; as mixers for heating water; in industrial heat engineering - in systems of fuel supply, combustion and air supply of furnaces, bench installations for testing engines; in ventilation installations - to create a continuous flow of air through channels and rooms; in plumbing installations - for lifting water from deep wells; for transportation of solid bulk materials and liquids.

Literature

1. Physics. Big Encyclopedic Dictionary.- M.: Big Russian Encyclopedia, 1999.- P.90, 460.

2. New Polytechnical Dictionary.- M.: Great Russian Encyclopedia, 2000.- S.20, 231, 460.

Keywords

• ejection
• capture
• flow
• flow rate
• turbulent boundary layer
• mixing
• pressure

Sections of natural sciences:

Ejection effect-1. The process of mixing any two media, in which one medium, being under pressure, affects the other and carries it in the required direction. 2. artificial restoration of water pressure during floods and long floods for the normal operation of turbines. A feature of the physical process - the mixing of flows occurs at high speeds of the ejecting (active) flow.

Applying an effect. Increasing the pressure of the ejected flow without direct mechanical energy is used in jet devices , which are used in various branches of technology:

in power plants in combustion devices(gas injection burners);

in the power supply system of steam boilers (anti-cavitation water jet pumps);

to increase the pressure from the turbine selections ( steam jet compressors);

for air suction from the condenser ( steam jet and water jet ejectors);

· in systems of air cooling of generators;

in heating installations;

· as mixers on heating waters;

in industrial heat engineering - in fuel supply, combustion and air supply systems for furnaces, bench installations for testing engines;

· in ventilating installations - for creation of a continuous stream of air through channels and rooms;

in plumbing installations - for lifting water from deep wells;

· for transportation of firm bulk materials and liquids.

gyroscope(or top) is a massive symmetrical body rotating at high speed around the axis of symmetry .
Gyroscopic effect - preservation, as a rule, directions axes of rotation freely and rapidly rotating bodies, accompanied under certain conditions, as precession (movement of an axis along a circular conical surface), and nutation (oscillatory movements (trembling) of the axis of rotation;

Centrifugal force- that force that, when a body moves along a curved line, causes the body to leave the curve and continue along the path tangentially to it. The centripetal force is opposite to the centripetal force, forcing a body moving along a curve to strive to approach the center; from the interaction of these two forces, the body receives a curvilinear motion.

Doppler effect - change in the frequency and wavelength recorded by the receiver, caused by the movement of their source and / or the movement of the receiver.

Application: determining the distance to the object, the speed of the object, the temperature of the object.

Diffusion- mutual penetration of adjoining substances due to the thermal motion of the particles of the substance. Diffusion takes place in gases, liquids and solids.

Application: in chemical kinetics and technology for regulating chemical reactions, in evaporation and condensation processes, for bonding substances.

hydrostatic pressure is the pressure at any point in a fluid at rest. It is equal to the sum of the pressure on the free surface (atmospheric) and the pressure of the liquid column located above the point under consideration. It is the same in all directions (Pascal's law). Determines the hydrostatic force (buoyancy force, support force) of the ship.

An ejector is a device that is designed to transfer kinetic energy from one medium moving at a higher speed to another. This device is based on the Bernoulli principle. This means that the unit is able to create a reduced pressure in the narrowing section of one medium, which, in turn, will cause suction into the flow of another medium. Thus, it is transferred, and then removed from the place of absorption of the first medium.

General information about the device

An ejector is a small but very efficient device that works in tandem with a pump. If we talk about water, then, of course, a water pump is used, but it can also work in tandem with steam, steam-oil, steam-mercury, and liquid-mercury pumps.

The use of this equipment is advisable if the aquifer lies quite deep. In such situations, it most often happens that conventional pumping equipment cannot cope with providing water to the house or it supplies too little pressure. The ejector will help solve this problem.

Kinds

An ejector is a fairly common equipment, and therefore there are several different types of this device:

• The first is steam. It is intended for exhausting gases and confined spaces, as well as for maintaining vacuum in these spaces. The use of these units is common in various technical industries.
• The second is a steam jet. This apparatus uses the energy of a steam jet, with the help of which it is able to suck liquid, steam or gas from an enclosed space. The steam that exits the nozzle at high speed entails the substance being moved. Most often used on various ships and ships for quick suction of water.
• A gas ejector is a device whose principle of operation is based on the fact that the excess pressure of high-pressure gases is used to compress low-pressure gases.

Water suction ejector

If we talk about the extraction of water, then the ejector for the water pump is most often used. The thing is that if after the water is lower than seven meters, then a conventional water pump will cope with great difficulty. Of course, you can immediately buy a submersible pump, the performance of which is much higher, but it is expensive. But with the help of an ejector, you can increase the power of an existing unit.

It should be noted that the design of this device is quite simple. The production of a homemade device also remains a very real task. But for this you will have to work hard on the drawings for the ejector. The basic principle of operation of this simple apparatus is that it imparts additional acceleration to the flow of water, which leads to an increase in the supply of liquid per unit of time. In other words, the task of the unit is to increase the pressure of water.

Elements

Installing an ejector will lead to the fact that the optimal level of water intake will greatly increase. The indicators will be approximately equal from 20 to 40 meters in depth. Another advantage of this particular device is that its operation requires much less electricity than, for example, a more efficient pump would require.

The pump ejector itself consists of such parts as:

• suction chamber;
• diffuser;
• narrowed nozzle.

Principle of operation

The principle of operation of the ejector is completely based on the Bernoulli principle. This statement says that if you increase the speed of any flow, then an area with low pressure will always form around it. Because of this, such an effect as discharge is achieved. The liquid itself will pass through the nozzle. The diameter of this part is always smaller than the dimensions of the rest of the structure.

It is important to understand here that even a slight narrowing will significantly accelerate the flow of incoming water. Next, the water will enter the mixer chamber, where it will create a reduced pressure. Due to the occurrence of this process, it will occur that a liquid will enter the mixer through the suction chamber, the pressure of which will be much higher. This is the principle of the ejector, if we describe it briefly.

It is important to note here that water should not enter the device from a direct source, but from the pump itself. In other words, the unit must be mounted in such a way that some of the water that rises with the pump remains in the ejector itself, passing through the nozzle. This is necessary in order to be able to supply constant kinetic energy to the mass of liquid that needs to be lifted.

Thanks to the work in this way, a constant acceleration of the flow of matter will be maintained. Of the advantages, it can be distinguished that the use of an ejector for the pump will save a large amount of electricity, since the station will not work at the limit.

Pump device type

Depending on the location, it can be built-in or remote type. There is no huge structural difference between the installation sites, however, some small differences will still make themselves felt, since the installation of the station itself will change slightly, as well as its performance. Of course, it is clear from the name that the built-in ejectors are installed inside the station itself or in its immediate vicinity.

This type of unit is good because you do not have to allocate additional space for its installation. The installation of the ejector itself will also not have to be carried out, since it is already built in, only the station itself will need to be installed. Another advantage of such a device is that it will be very well protected from various kinds of pollution. The disadvantage is that this type of device will create a lot of noise.

Model comparison

Remote equipment will be somewhat more difficult to install and you will have to allocate a separate place for its location, however, the amount of noise, for example, will decrease significantly. But there are other shortcomings here. Remote models are able to provide effective operation only at a depth of up to 10 meters. Built-in models are initially designed for not too deep sources, but the advantage is that they create a fairly powerful pressure, which leads to more efficient use of the liquid.

The created jet is quite enough not only for domestic needs, but also for operations such as watering, for example. The increased noise level from the built-in model is one of the most significant problems that will have to be taken care of. Most often, it is solved by installing it together with the ejector in a separate building or in a well caisson. You will also have to take care of a more powerful electric motor for such stations.

Connection

If we talk about connecting a remote ejector, you will have to perform the following operations:

• Laying an additional pipe. This object is necessary in order to ensure the circulation of water from the pressure line to the water intake.
• The second step is to connect a special branch pipe to the suction port of the water intake station.

But connecting the built-in unit will not differ in any way from the usual process of installing a pumping station. All necessary procedures for connecting the necessary pipes or nozzles are carried out at the factory.

Ejector - what is it? Description, device, types and features. What is the difference between injection and ejection

injection

INJECTION (a. injection; n. Injection, Einspritzung; f. injection; and. inyeccion) - the process of continuous mixing of two streams of substances and the transfer of energy from the injecting (working) stream to the injected one with the aim of injecting it into various devices, tanks and pipelines. The mixed flows can be in the gas, vapor and liquid phases and be equal-phase, different-phase and changing phase (for example, steam-water). The jet devices (pumps) used for injection are called injectors. The injection phenomenon has been known since the 16th century. From the beginning of the 19th century the injection process has been industrially used to increase the draft in the chimneys of steam locomotives.

The foundations of the theory of injection were laid in the works of the German scientist H. Zeiner and the English scientist W. J. M. Rankin in the 1970s. 19th century In the USSR, beginning in 1918, a significant contribution to the development of the theory and practice of injection was made by A. Ya. Milovich, N. I. Galperin, S. A. Khristianovich, E. Ya. of injected flows with different speeds is accompanied by a significant loss of kinetic energy per impact and its transformation into thermal energy, equalization of velocities, and an increase in the pressure of the injected flow. The injection is described by the laws of conservation of energy, mass, and momentum. In this case, the energy loss per impact is proportional to the square of the difference in flow rates at the beginning of mixing. If it is necessary to quickly and thoroughly mix two homogeneous media, the mass velocity of the working stream should exceed the mass velocity of the injected one by 2-3 times. In some cases, during injection, along with a hydrodynamic process, a thermal process also occurs with the transfer of thermal energy to the injected thermal energy, for example, when liquids are heated by steam with intensive mixing of the media - liquid and condensate.

The principle of injection is that the pressure P1 and the average linear velocity u1 of the injecting (working) flow of gas or liquid moving through the pipe change in the narrowed section. The flow rate increases (u2>u1), pressure (P2<Р1) падает, т.е. рост кинетической энергии потока сопровождается уменьшением его потенциальной энергии. При падении давления Р2 ниже давления Р0 в суженную часть трубы засасывается инжектируемая среда, которая за счёт поверхностного трения увлекается рабочим потоком и смешивается с ним. При дальнейшем движении смеси по трубе с расширяющимся сечением уменьшение скорости потока до 3 и его кинетической энергии сопровождается нарастанием потенциальной энергии и давления до величины Р3, причём Р2<Р0<Р3<Р1. Таким образом, в результате инжекционное давление инжектируемой среды возрастает от Р0 до Р3 за счёт падения давления рабочего потока от Р1 до Р3, а давление смешанного потока приобретает промежуточное значение.

In the case of injection with changing phases of the media, for example, with condensation of the working vapor from contact with the cold injected liquid, it is possible to create a mixed flow pressure that exceeds the pressure of the working flow. In this case, the work expended on the injection is performed not only by the energy of the jet, but also by external pressure when the volume of the condensing working vapor is reduced, and also due to the conversion of its thermal energy into the potential energy of the mixed flow. Compared to mechanical methods of mixing, heating, compressing and pumping various media, injection is simple, but requires 2-3 times more energy. See the Injector article for more information on how to use injection.

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principle of operation and device of the ejector pump

Ejector - what is it? This question often arises among the owners of country houses and cottages in the process of arranging an autonomous water supply system. The source of water in such a system, as a rule, is a pre-drilled well or well, the liquid from which must not only be raised to the surface, but also transported through a pipeline. To solve such problems, a whole technical complex is used, consisting of a pump, a set of sensors, filters and a water ejector, installed if the liquid from the source must be pumped out from a depth exceeding ten meters.

When do you need an ejector?

Before dealing with the question of what an ejector is, you should find out why you need a pumping station equipped with it. In essence, an ejector (or ejector pump) is a device in which the energy of motion of one medium moving at high speed is transferred to another medium. Thus, at an ejector pumping station, the principle of operation is based on Bernoulli's law: if a reduced pressure of one medium is created in the tapering section of the pipeline, this will cause a suction of another medium into the formed flow and its transfer from the suction point.

Everyone is well aware that the greater the depth of the source, the harder it is to raise water from it to the surface. As a rule, if the depth of the source is more than seven meters, then a conventional surface pump can hardly perform its functions. Of course, a more efficient submersible pump can be used to solve such a problem, but it is better to go the other way and purchase an ejector for a surface-type pumping station, significantly improving the characteristics of the equipment used.

Due to the use of a pumping station with an ejector, the pressure of the liquid in the main pipeline increases, while the energy of the fast flow of the liquid medium flowing through its separate branch is used. Ejectors, as a rule, work in a set with jet-type pumps - water-jet, liquid-mercury, mercury vapor and oil-steam.

An ejector for a pumping station is especially relevant if it is necessary to increase the capacity of an already installed or planned station with a surface pump. In such cases, the ejector installation allows you to increase the depth of water intake from the reservoir up to 20-40 meters.

Overview and operation of a pumping station with an external ejector

Types of ejector devices

According to their design and principle of operation, jet pumps can belong to one of the following categories.

With the help of such ejector devices, gaseous media are pumped out of confined spaces, and a rarefied state of air is also maintained. Devices operating on this principle have a wide range of applications.

Steam jet

In such devices, the energy of a steam jet is used to suck gaseous or liquid media from a closed space. The principle of operation of this type of ejector lies in the fact that steam flying out of the installation nozzle at high speed entrains the transported medium leaving through the annular channel located around the nozzle. Ejector pumping stations of this type are used mainly for the rapid pumping of water from the premises of ships for various purposes.

Stations with an ejector of this type, the principle of operation of which is based on the fact that the compression of a gaseous medium, initially under low pressure, occurs due to high-pressure gases, are used in the gas industry. The described process takes place in the mixing chamber, from where the flow of the pumped medium is directed to the diffuser, where it slows down, and hence the pressure increases.

Design features and principle of operation

The design elements of a remote ejector for a pump are:

• a chamber into which the pumped medium is sucked;
• mixing unit;
• diffuser;
• nozzle, the cross section of which is narrowed.

How does any ejector work? As mentioned above, such a device operates according to the Bernoulli principle: if the speed of the flow of a liquid or gaseous medium increases, then an area characterized by low pressure is formed around it, which contributes to the rarefaction effect.

So, the principle of operation of a pumping station equipped with an ejector device is as follows:

• The liquid medium pumped by the ejector unit enters the latter through a nozzle whose cross section is smaller than the diameter of the inlet line.
• Passing into the mixer chamber through a nozzle with a decreasing diameter, the flow of the liquid medium acquires a noticeable acceleration, which contributes to the formation of a region with reduced pressure in such a chamber.
• Due to the rarefaction effect in the ejector mixer, a liquid medium at a higher pressure is sucked into the chamber.

If you decide to equip a pumping station with a device such as an ejector, keep in mind that the pumped liquid medium does not enter it from a well or well, but from a pump. The ejector itself is located in such a way that part of the liquid that was pumped out of the well or well by means of a pump returns to the mixer chamber through a tapering nozzle. The kinetic energy of the liquid flow entering the mixer chamber of the ejector through its nozzle is transferred to the mass of the liquid medium sucked by the pump from the well or well, thereby ensuring a constant acceleration of its movement along the inlet line. Part of the fluid flow, which is pumped out by a pumping station with an ejector, enters the recirculation pipe, and the rest enters the water supply system serviced by such a station.

Once you understand how a pumping station equipped with an ejector works, you will realize that it requires less energy to raise water to the surface and transport it through a pipeline. Thus, not only the efficiency of using pumping equipment is increased, but also the depth from which the liquid medium can be pumped out increases. In addition, when using an ejector that sucks up liquid on its own, the pump is protected from running dry.

The device of a pumping station with an ejector provides for the presence in its equipment of a crane installed on the recirculation pipe. With the help of such a valve, which regulates the flow of fluid entering the ejector nozzle, you can control the operation of this device.

Types of ejectors at the installation site

When purchasing an ejector to equip a pumping station, keep in mind that such a device can be built-in and external. The device and principle of operation of these two types of ejectors are practically the same, the differences are only in the place of their installation. Built-in ejectors can be placed in the inside of the pump housing, or mounted in close proximity to it. The built-in ejection pump has a number of advantages, which include:

• minimum space required for installation;
• good protection of the ejector from contamination;
• no need to install additional filters that protect the ejector from insoluble inclusions contained in the pumped liquid.

Meanwhile, it should be borne in mind that built-in ejectors demonstrate high efficiency if they are used to pump water from sources of shallow depth - up to 10 meters. Another significant disadvantage of pumping stations with built-in ejectors is that they emit quite a lot of noise during their operation, so it is recommended to locate them in a separate room or in a caisson of an aquifer. It should also be borne in mind that the device of this type of ejector involves the use of a more powerful electric motor that drives the pumping unit itself.

A remote (or external) ejector, as its name implies, is installed at a certain distance from the pump, and it can be quite large and reach up to fifty meters. Remote-type ejectors, as a rule, are placed directly in the well and connected to the system through a recirculation pipe. A pumping station with a remote ejector also requires the use of a separate storage tank. This tank is necessary in order to ensure the constant availability of water for recirculation. The presence of such a tank, in addition, allows you to reduce the load on the pump with a remote ejector, and reduce the amount of energy required for its operation.

The use of remote-type ejectors, the efficiency of which is somewhat lower than that of built-in devices, makes it possible to pump out a liquid medium from wells of considerable depth. In addition, if you make a pumping station with an external ejector, then it can not be placed in the immediate vicinity of the well, but mounted at a distance from the source of water intake, which can be from 20 to 40 meters. At the same time, it is important that the location of pumping equipment at such a considerable distance from the well will not affect the efficiency of its operation.

Production of an ejector and its connection to pumping equipment

Having figured out what an ejector is and having studied the principle of its operation, you will understand that you can make this simple device with your own hands. Why make an ejector with your own hands, if it can be purchased without any problems? It's all about saving. Finding drawings according to which you can make such a device yourself is not a problem, and for its manufacture you will not need expensive consumables and sophisticated equipment.

How to make an ejector and connect it to a pump? For this purpose, you need to prepare the following components:

• tee with internal thread;
• union;
• couplings, elbows and other fitting elements.

The manufacture of the ejector is carried out according to the following algorithm.

1. A fitting is screwed into the lower part of the tee, and this is done so that the narrow branch pipe of the latter is inside the tee, but does not protrude from its reverse side. The distance from the end of the narrow branch pipe of the fitting to the upper end of the tee should be about two to three millimeters. If the fitting is too long, then the end of its narrow pipe is ground off, if it is short, then it is increased with a polymer tube.
2. An adapter with an external thread is screwed into the upper part of the tee, which will be connected to the suction line of the pump.
3. A branch in the form of a corner is screwed into the lower part of the tee with an already installed fitting, which will be connected to the recirculation pipe of the ejector.
4. A bend in the form of a corner is also screwed into the side branch pipe of the tee, to which a pipe supplying water from the well is connected by means of a collet clamp.

All threaded connections made in the manufacture of a homemade ejector must be tight, which is ensured by the use of FUM tape. On the pipe through which water will be taken from the source, a check valve and a strainer should be placed, which will protect the ejector from clogging. As pipes, with the help of which the ejector will be connected to the pump and the storage tank, which ensures the recirculation of water in the system, you can choose products made of both metal-plastic and polyethylene. In the second variant, not collet clamps are needed for installation, but special crimp elements.

After all the required connections are made, a homemade ejector is placed in the well, and the entire pipeline system is filled with water. Only then can the first start-up of the pumping station be carried out.

What is it? Description, device, types and features

An ejector is a device that is designed to transfer kinetic energy from one medium moving at a higher speed to another. This device is based on the Bernoulli principle. This means that the unit is able to create a reduced pressure in the narrowing section of one medium, which, in turn, will cause suction into the flow of another medium. Thus, it is transferred, and then removed from the place of absorption of the first medium.

General information about the device

An ejector is a small but very efficient device that works in tandem with a pump. If we talk about water, then, of course, a water pump is used, but it can also work in tandem with steam, steam-oil, steam-mercury, and liquid-mercury pumps.

The use of this equipment is advisable if the aquifer lies quite deep. In such situations, it most often happens that conventional pumping equipment cannot cope with providing water to the house or it supplies too little pressure. The ejector will help solve this problem.

Kinds

An ejector is a fairly common equipment, and therefore there are several different types of this device:

• The first is steam. It is intended for exhausting gases and confined spaces, as well as for maintaining vacuum in these spaces. The use of these units is common in various technical industries.
• The second is a steam jet. This apparatus uses the energy of a steam jet, with the help of which it is able to suck liquid, steam or gas from an enclosed space. The steam that exits the nozzle at high speed entails the substance being moved. Most often used on various ships and ships for quick suction of water.
• A gas ejector is a device whose principle of operation is based on the fact that the excess pressure of high-pressure gases is used to compress low-pressure gases.

Water suction ejector

If we talk about the extraction of water, then the ejector for the water pump is most often used. The thing is that if, after drilling a well, the water is lower than seven meters, then an ordinary water pump will cope with great difficulty. Of course, you can immediately buy a submersible pump, the performance of which is much higher, but it is expensive. But with the help of an ejector, you can increase the power of an existing unit.

It should be noted that the design of this device is quite simple. The production of a homemade device also remains a very real task. But for this you will have to work hard on the drawings for the ejector. The basic principle of operation of this simple apparatus is that it imparts additional acceleration to the flow of water, which leads to an increase in the supply of liquid per unit of time. In other words, the task of the unit is to increase the pressure of water.

Elements

Installing an ejector will lead to the fact that the optimal level of water intake will greatly increase. The indicators will be approximately equal from 20 to 40 meters in depth. Another advantage of this particular device is that its operation requires much less electricity than, for example, a more efficient pump would require.

The pump ejector itself consists of such parts as:

Principle of operation

The principle of operation of the ejector is completely based on the Bernoulli principle. This statement says that if you increase the speed of any flow, then an area with low pressure will always form around it. Because of this, such an effect as discharge is achieved. The liquid itself will pass through the nozzle. The diameter of this part is always smaller than the dimensions of the rest of the structure.

It is important to understand here that even a slight narrowing will significantly accelerate the flow of incoming water. Next, the water will enter the mixer chamber, where it will create a reduced pressure. Due to the occurrence of this process, it will occur that a liquid will enter the mixer through the suction chamber, the pressure of which will be much higher. This is the principle of the ejector, if we describe it briefly.

It is important to note here that water should not enter the device from a direct source, but from the pump itself. In other words, the unit must be mounted in such a way that some of the water that rises with the pump remains in the ejector itself, passing through the nozzle. This is necessary in order to be able to supply constant kinetic energy to the mass of liquid that needs to be lifted.

Thanks to the work in this way, a constant acceleration of the flow of matter will be maintained. Of the advantages, it can be distinguished that the use of an ejector for the pump will save a large amount of electricity, since the station will not work at the limit.

Pump device type

Depending on the installation location of the unit, it can be built-in or remote type. There is no huge structural difference between the installation sites, however, some small differences will still make themselves felt, since the installation of the station itself will change slightly, as well as its performance. Of course, it is clear from the name that the built-in ejectors are installed inside the station itself or in its immediate vicinity.

This type of unit is good because you do not have to allocate additional space for its installation. The installation of the ejector itself will also not have to be carried out, since it is already built in, only the station itself will need to be installed. Another advantage of such a device is that it will be very well protected from various kinds of pollution. The disadvantage is that this type of device will create a lot of noise.

Model comparison

Remote equipment will be somewhat more difficult to install and you will have to allocate a separate place for its location, however, the amount of noise, for example, will decrease significantly. But there are other shortcomings here. Remote models are able to provide effective operation only at a depth of up to 10 meters. Built-in models are initially designed for not too deep sources, but the advantage is that they create a fairly powerful pressure, which leads to more efficient use of the liquid.

The created jet is quite enough not only for domestic needs, but also for operations such as watering, for example. The increased noise level from the built-in model is one of the most significant problems that will have to be taken care of. Most often, it is solved by the fact that the pumping station, together with the ejector, is installed in a separate building or in the well's caisson. You will also have to take care of a more powerful electric motor for such stations.

Connection

If we talk about connecting a remote ejector, you will have to perform the following operations:

• Laying an additional pipe. This object is necessary in order to ensure the circulation of water from the pressure line to the water intake.
• The second step is to connect a special branch pipe to the suction port of the water intake station.

But connecting the built-in unit will not differ in any way from the usual process of installing a pumping station. All necessary procedures for connecting the necessary pipes or nozzles are carried out at the factory.

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EJECTION AND INJECTION OF REAGENTS IN WATER TREATMENT TECHNOLOGIES | Publish article RSCI

Petrosyan O.P.1, Gorbunov A.K.2, Ryabchenkov D.V.3, Kulyukina A.O.4

1Candidate of Physical and Mathematical Sciences, Associate Professor, Kaluga Branch of the Federal State Budgetary Educational Institution of Higher Professional Education “Moscow State Technical University named after N.E. Bauman (National Research University)" (KF MSTU named after N.E. Bauman), 2Doctor of Physical and Mathematical Sciences, Professor, Kaluga Branch of the Federal State Budgetary Educational Institution of Higher Professional Education "Moscow State Technical University named after N.E. Bauman (National Research University)" (KF MSTU named after N.E. Bauman), 3Postgraduate student, Kaluga Branch of the Federal State Budgetary Educational Institution of Higher Professional Education "Moscow State Technical University named after N.E. Bauman (National Research University)" (KF MSTU named after N.E. Bauman), 4Postgraduate student, Kaluga Branch of the Federal State Budgetary Educational Institution of Higher Professional Education "Moscow State Technical University named after N.E. Bauman (National Research University)" (KF MSTU named after N.E. Bauman)

EJECTION AND INJECTION OF REAGENTS IN WATER TREATMENT TECHNOLOGIES

annotation

The water treatment system provides for the introduction of various reagents into it. The main technological methods for introducing reagents into disinfected water are ejection and injection. This article analyzes these methods. A method for calculating high-performance ejectors has been developed. The laboratory and production tests carried out by the authors established the optimal ratio of the longitudinal dimensions of the internal section, providing the most effective value of the ejection coefficient.

Key words: ejector, diffuser, mixing chamber, ejection coefficient, aeration, chlorination.

Petrosyan O.P.1, Gorbunov A.K.2, Ryabchenkov D.V.3, Kuliukina A.O. 4

1PhD in Physics and Mathematics, Associate Professor, 2PhD in Physics and Mathematics, Professor, 3Postgraduate Student, 4Postgraduate Student, Kaluga Branch of the Federal State Budget Educational Institution of Higher Professional Education “Bauman Moscow State Technical University (National Research University” (Kaluga Branch) of Moscow State Technical University named after N.E. Bauman)

EJECTION AND INJECTION OF REAGENTS IN WATER TREATMENT TECHNOLOGIES

A water treatment system provides for the introduction of various reagents into it. The main technological methods for introducing reagents into disinfected water are ejection and injection. This article analyzes both of these methods. A technique for calculating high-efficiency ejectors is developed. The laboratory and production tests carried out by the authors established the best proportions of the internal section longitudinal dimensions – they ensure the maximum effective value of the ejection coefficient.

Keywords: ejector, diffuser, mixing chamber, ejection coefficient, aeration, chlorination.

Drinking water centrally supplied to the population must comply with SanPin 2.1.4.559-96. This water quality is achieved, as a rule, by using the classical two-stage scheme shown in Figure 1. At the first stage, coagulants and flocculants are introduced into the treated water and then clarification is carried out in horizontal settling tanks and quick filters, at the second stage, before being fed into the CWR, disinfection is performed. .

Rice. 1 - Technological scheme of the water treatment system

Thus, the scheme provides for the introduction of various reagents into the water in the form of gases (chlorine, ozone, ammonia, chlorine dioxide), hypochlorite solutions, coagulants (aluminum sulphate and / or aluminum hydroxochloride), flocculants (PAA, Praistol and Fennopol). Most often, dosing and supply of these reagents is carried out by injection or ejection.

Injection is the introduction and spraying through the nozzle (injector) of solutions of chlorine water, hypochlorite, coagulant (flocculant) by pressure pumps.

Ejector - "ejection pump" sets in motion a solution of a reagent or gas by rarefying the medium. The vacuum is created by the working (active) flow moving at a higher speed. This active flow is called ejecting, and the mixture set in motion is called ejected (passive mixture). In the mixing chamber of the ejector, the passive mixture transfers energy to the active flow, as a result of which all their indicators, including speeds.

The widespread use of the ejection process is justified by the following factors: the simplicity of the device and its maintenance; low wear due to the absence of rubbing parts, which leads to a long service life. That is why ejection is used in many complex technical devices, such as: chemical reactors; degassing and aeration systems; gas transportation installations, drying and evacuation; heat transfer systems; and, of course, as mentioned above in the systems of water treatment and water supply.

The limitation in the use of injectors in the same systems is due to their low productivity, since high productivity requires powerful injector pumps, which leads to a significant increase in the cost of the system, while increasing productivity by ejectors is less expensive. Thus, automatic modular water treatment stations, designed to supply drinking water to small villages, overwhelmingly use injection. A typical design of such a universal type station is presented in, where injection is used at all points for introducing reagents into water. Often they make a compromise solution (Fig. 2). At the first stage, the so-called chlorine water is obtained by ejection of gaseous chlorine into water using chlorinators in the ejector 4, which is then (at the second stage) injected by pump 1 into conduit 2, where the flow of treated water moves.

Rice. 2 - Ejection and injection of gaseous chlorine into water

Rice. 3 - Scheme of the input of chlorine water in the process of its injection into the conduit

A typical injection unit for introducing chlorine water into conduit 2 in such cases is shown in Fig.3. The advantage of such a scheme is the rational combination of ejection and injection, which allows, thanks to the pump 1, necessary for the implementation of the injection, to provide a high ejection performance of the ejector. Diagrams for choosing pump 1 in such schemes for an ejector with a capacity of up to 20 kg Сl/h are shown in fig. 4.

On fig. 5 shows a typical design of the ejector, which is most typical for dosing a gas reagent (most often chlorine) into a water conduit. The ejector consists of an ejecting flow (water) supply line, which is a cone-shaped nozzle 1, which is connected to a mixing chamber (working chamber) 2 and a mixing chamber 4. The ejected gaseous chlorine is supplied to the working chamber 2 through the device 3. The diffuser 5 supplies chlorine water to the conduit .

Rice. 4 - Diagram of pump selection to the ejector 20kg Gl/h

The parameters of such an ejector are the initial values ​​that determine all the main operating parameters of the reagent inlet units. The authors have developed a method for calculating high-performance chlorinators based on which a model range of ejectors of various capacities has been developed and patented.

The performance and other characteristics of the injector, which is actually a dosing pump, depend on the overall technical characteristics of the pump itself and the pulse dosing system. The main characteristics of the ejector determine the design features of its cross section, and these features are so fundamental that it is almost impossible to ensure the efficiency of the ejector without technical calculations and experimental studies. Therefore, it is advisable to consider these issues using the example of ejectors for dosing gaseous chlorine into water.

Thus, the action of the ejector is based on the transfer of the kinetic energy of the ejecting flow (active flow) of the liquid, which has a large amount of energy, to the ejected (passive) flow, which has a small amount of energy , . We write the Bernoulli equation for an ideal fluid in accordance with which the sum of specific potential energy (static head) and specific kinetic energy (velocity head) is constant and equal to the total head:

Rice. 5 - Ejector for dosing gaseous chlorine into water

The water flowing out of the nozzle has a higher speed (v2>v1), i.e., a large velocity head, therefore, the piezometric head of the water flow in the working chamber 2 and in the mixing chamber decreases (p2

The ratio of the flow rate of the ejected fluid (QE) to the flow rate of the working fluid (QP) is called the mixing or ejection coefficient - a.

The ejection coefficient, which depends on the parameters of the ejector, lies in a fairly wide range from 0.5 to 2.0. The most stable operation of the water jet pump is observed at a=1.

The pressure coefficient of the ejector pump ß is the ratio of the total geometric lift height (H) of the ejected fluid flow in meters - this is the pressure at the inlet to the ejector to the head of the working flow (h) in m - counterpressure.

An important parameter that characterizes the efficiency of the ejector and also depends on the design parameters of the device is the efficiency of the pump. As you know, this coefficient is equal to the ratio of useful power expended (H QE Y kGm / s) to the consumed power (h QP Y kGm / s), that is

Thus, the efficiency of the ejection pump is determined by the product of the pressure and ejection coefficients. Laboratory experiments on the stand were carried out to determine the pressure coefficient of ejectors of various capacities. The resulting experimental diagram of the ejector is shown in Fig.3. According to this diagram, the parameters are determined - the pressure at the inlet to the ejector, the back pressure and the flow rate of the ejecting fluid, which provide the flow rate of the ejected gas of 20 kg/h.

In accordance with the obtained method for calculating the parameters of the ejector, the basic standard sizes of the ejectors of the chlorinator model range with a chlorine capacity from 0.01 kg/h to 200 kg/h were determined, providing the maximum ejection capacity. It has been established that the configuration of the internal longitudinal section of the ejector must take into account the following section dimensions (Fig. 5): nozzle diameter D, working chamber length L, mixing chamber diameter D1, mixing chamber length L1, diffuser outlet diameter D2, diffuser length L2.

An experimental confirmation of the dependence of chlorine consumption Q on water consumption R is obtained. The curve Q = f(R) is approximated by two straight lines, the intersection of which separates the effective ejection zone with a high ejection coefficient from the inefficient zone. Obviously, the area of ​​effective ejection is of further interest, and the design of the internal section of the ejector should be such that the ejection coefficient in this area is the maximum possible.

The area in which the ejection coefficient changes is determined by the geometric parameter of the ejector m, equal to the ratio of the cross-sectional area of ​​the mixing chamber F to the cross-sectional area of ​​the nozzle F1:

Thus, this parameter is the main one by which all other main dimensions of the ejection pump are calculated.

An analysis of the results obtained from a comparison of experimental results with existing analytical data allows us to draw the following conclusions. The most efficient ejection of the pump corresponds to the parameter m lying in the range of 1.5 - 2.0. In this case, the mixing chamber diameter D1 = D determined by the formula, at D = 7 mm lies in the range of 8.6 -10 mm.

The proportion linking all the parameters indicated in Fig. 5 L = 1.75D, L1 = 1.75D, L2 = 7.75D was experimentally established. These ratios provide the maximum ejection coefficient, which lies in the region of the most efficient ejection.

Thus, we can conclude that in order to achieve maximum ejection, the design of the internal longitudinal section and the size ratios must correspond to the found relationships D1=1.25D, D2=2.5D, L=1.75D, L1=1.75D, L2=7 .75D

The ejection pump designed according to these ratios creates optimal conditions for transferring the kinetic energy of the ejecting liquid entering the pump inlet under high pressure, determined from the diagram, the ejected gas supplied to the mixing chamber with a lower velocity head and a lower energy reserve and provides maximum gas suction.

References / References

1. A. B. Kozhevnikov. Modern automation of reagent technologies for water treatment / A. B. Kozhevnikov, O. P. Petrosyan // Stroyprofil. - 2007. - No. 2. - P. 36 - 38.
2. Pat. 139649 Russian Federation, MPK C02F Automatic modular water treatment station with a system for bottling and selling drinking water of improved taste / Kozhevnikov A. B. Petrosyan A. O., Paramonov S. S.; publ. 04/20/2014.
3. A. B. Kozhevnikov. Modern equipment for chlorination water treatment stations / A. B. Kozhevnikov, O. P. Petrosyan // ZhKH. - 2006. - No. 9. - P. 15 - 18.
4. Bakhir V. M. On the problem of finding ways to improve the industrial and environmental safety of water treatment and sanitation facilities / Bakhir V. M. // Water supply and sewerage. - 2009. - No. 1. - P. 56 - 62.
5. A. B. Kozhevnikov, O. P. Petrosyan. Ejection and drying of materials in the mode of pneumatic transport. - M: Publishing house of MSTU im. N. E. Bauman. - 2010. - C. 142.
6. Pat. 2367508 Russian Federation, MPK C02F Ejector for dosing gaseous chlorine into water / A. B. Kozhevnikov, O. P. Petrosyan; publ. 09/20/2009.
7. A. S. Volkov, A. A. Volokitenkov. Drilling wells with reverse circulation of drilling fluid. - M: Nedra Publishing House. - 1970. - S. 184.

References in English / References in English

1. A. B. Kozhevnikov. Sovremennaja avtomatizacija reagentnyh tehnologij vodopodgotovki / A. B. Kozhevnikov, O. P. Petrosjan // Strojprofil’ . - 2007. - No. 2. - P. 36 - 38.
2. Bahir V. M. K probleme poiska putej povyshenija promyshlennoj i jekologicheskoj bezopasnosti ob#ektov vodopodgotovki i vodootvedenija ZhKH / Bahir V. M. // Vodosnabzhenie i kanalizacija . - No. 1. - R. 56 - 62.
3. 139649 Russian Federation, MPK C02F9. Avtomaticheskaja modul'naja stancija vodopodgotovki s sistemoj rozliva i prodazhi pit'evoj vody uluchshennogo vkusovogo kachestva / A. B. Kozhevnikov, A. O. Petrosjan, S. S. Paramonov.; Publ. 04/20/2014.
4. B. Kozhevnikov. Sovremennoe oborudovanie hloratornyh stancij vodopodgotovki / A. B. Kozhevnikov. // ZhKH. - 2006. - No. 9. - P. 15 - 18.
5. Bahir V. M. K / Bahir V. M. // Vodosnabzhenie i kanalizacija. - 2009. - No. 1. - P. 56 - 62.
6. Kozhevnikov, O. P. Petrosjan. Jezhekcija i sushka materialov v rezhime pnevmotransporta. M: Izd-vo MGTU im. N. Je. Bauman. - 2010. - P. 142.
7. 2367508 Russian Federation, MPK C02F9. Jezhektor dlja dozirovanija gazoobraznogo hlora v vodu / A. B. Kozhevnikov, A. O. Petrosjan; Publ. 09/20/2009.
8. Volkov, A. A. Volokitenkov. Burenie skvazhin s obratnoj cirkuljaciej promyvochnoj zhidkosti . M: Izd-vo Nedra. - 1970. - P.184.

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Principle - ejection - The Big Encyclopedia of Oil and Gas, article, page 1

Principle - ejection

Page 1

The principle of ejection is as follows: a jet of injecting gas, leaving the nozzle at high speed, creates a rarefaction and entrains the ejected gas from the surrounding space.

The principle of ejection is used in gas burners for sucking in and mixing gas and air, in devices for removing exhaust gases, in steam-jet devices that supply air for combustion and gasification. To reduce losses, ejection devices are made multi-stage; in this case, the sucked-in medium is also ejected by the mixture of media.

The principle of ejection is simple: a fan is installed in a separate room, which creates a high-speed air pressure; when leaving a narrow nozzle, a jet of clean air takes the explosive mixture with it and throws it into the atmosphere. Ejection installations (Fig. 20) have a low efficiency and are used in cases where a better solution cannot be found.

It is on the principle of ejection that the movement of sand inside the pneumogenerator is built. Getting into the gap between the mouth of the pipe and the nozzle, through which air is supplied with a pressure of 0 2 - 0 3 kgf / cm2, sand particles and intergrowths of grains up to 2 5 mm in size are carried away by the air flow, accelerate and fly out at high speed upwards. When leaving the pipe, the sand-air flow encounters a baffle plate, on the inner surface of which a layer of sand is retained, which plays a dual role. Taking the impact of the flow on itself, the sand protects the shield from premature wear. On the other hand, when flowing around from the inner surface of the baffle shield, sand particles, moving at different speeds in different layers of the flow, rub against one another. As a result of friction, the intergrowths of grains disintegrate, individual grains are freed from films and clay shells and, in this case, acquire a rounded shape. The cleaned sand is discharged into the receiver, and the air, having lost a significant part of its speed, leaves through the curtain of falling sand, carrying away dust and small grains of quartz.

During the operation of the second type of hydraulic mixers, the ejection principle is used, which consists in the effect of lowering the pressure around the liquid jet flowing out of the nozzle at high speed. As a result, clay powder is sucked into the rarefaction zone. The resulting pulp enters the tank and hits a special shoe, which contributes to the intensive mixing of clay with water.

The powder feeder of the UENP unit works on the principle of powder ejection from a fluidized bed. It is a cylindrical vessel with a porous partition through which compressed air is supplied to fluidize the powder. Additional fluidization of the powder is achieved by an eccentric type vibrator. To feed the powder into the sprayer, the feeder has an ejector. A control panel is fixed on the body of the feeder, on which gearboxes, valves, toggle switches are placed.

The work of the apn-arat with a jet mixer is based on the principle of ejection with some features inherent in these devices. The paper presents methods for calculating the reactor with a jet mixer.

Ventilation units based on the principle of ejection are considered safer.

The elevator, which is a water jet pump, works on the principle of ejection.

The selection of crystals is carried out on drums with steam jet pumps operating on the principle of ejection. The temperature of the evaporated bath entering the mold is 40 - 45 C, and as a result of the operation of the steam jet pumps, it decreases to 16 C. The cooled bath enters the second mold, where the temperature is further reduced to 10 C.

At some enterprises, chamber dryers are used for pre-drying and preheating of raw materials, which at the same time are containers of a loading device operating on the principle of pneumatic ejection. These dryers are installed in the immediate vicinity of injection molding or extrusion machines and serve several pieces of equipment at the same time.

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Injector (the term comes from the French injecteur, and it, in turn, from the Latin injicio - “throw in”): 1. An accelerator, and usually a linear accelerator, which is used to introduce charged particles into the main accelerator. In this case, the energy that is imparted to all particles inside the injector must be greater than the minimum required to start the operation of the main accelerator.

2. A jet pump, which is designed to compress gas or steam, as well as to inject liquids into various apparatuses or a reservoir. Injectors are used on steam locomotives, as well as inside locomotives and small boiler plants in order to supply feed water into the steam boiler. The advantage of injectors is that they do not have any moving parts and maintenance is very simple. The action of the injector is based on the transformation of the kinetic energy possessed by a steam jet into another type of energy - into the potential energy of water. At the same time, three cones are placed on the same axis inside the common injector chamber. Steam is supplied to the first steam cone by means of a steam pipeline from the boiler, which develops a high speed at the mouth of the first cone, and water is captured, which is supplied through the pipe from the tank. Subsequently, the resulting mixture, consisting of water and condensed steam, is driven into the water (or condensation) cone, from it into the discharge cone, then through the check valve into the steam boiler. The expanding cone reduces the speed of water flow in it, so the pressure increases and eventually becomes quite sufficient to overcome the pressure inside the steam boiler and pump feed water into the boiler. Excess water, which is formed at the very beginning of the injector operation, is then discharged through the valve of the "vest" pipe. It should also be taken into account that the temperature of the water that enters the injector should not exceed 40 ° C, while the suction height should not exceed 2.5 m. The injector can be installed both vertically and horizontally.

Steam injectors. Features of the process in a steam-water injector. In steam-water injectors, the pressure of the liquid is increased due to the kinetic energy of the steam jet, which, in the process of mixing with the liquid, is completely condensed in it.

A feature of this process, in contrast to the processes in other jet devices, is the possibility, under certain conditions, of increasing the pressure of the injected water to a value exceeding the pressure of the working steam. Thanks to this, steam-water injectors have been used since the middle of the 19th century. are widely used as feed pumps for small boilers. The low efficiency of these devices was not of particular importance, since the heat of the working steam with feed water was returned to the boiler. As the analysis showed, with an inverse ratio, the pressure of the mixed flow, in principle, can be obtained from any of the interacting flows only if the reversible mixing line passes through regions of higher isobars compared to the isobars of the state of the interacting media.

In jet devices, in the presence of irreversible impact losses during the interaction of flows with personal velocities, an increase in the entropy of the flow takes place compared to reversible mixing, which leads to a change in the pressure of the mixed flow. With regard to steam-water injectors, the possibility of obtaining a pressure exceeding the pressure of the operating media has been implemented in practice. This possibility exists due to the balance of work obtained from the working steam and the compression of the injected water. Recently, in connection with the development of a magnetohydrodynamic method for generating electricity, as well as thermal cycles with new working fluids, interest has increased in the use of injectors in these installations as jet condensers and pumps. Numerous studies of these devices have appeared, aimed at increasing their efficiency by reducing losses in the elements of the flow part of the injector, studying the conditions for their launch, etc. Many of these works have been generalized. Sufficiently complex designs of industrial injectors are described in detail.

In all designs, the injected water is supplied through a narrow annular slot surrounding the working nozzle, so that water enters the mixing chamber at a high speed, directed parallel to the speed of the working steam coming from the central Laval nozzle located on the axis of the injector. The mixing chamber has, as a rule, a conical shape. When conducting research on steam-water injectors, the task of developing the optimal shape of the flow path was not set. A method for calculating a steam-water injector of the simplest form (with a cylindrical mixing chamber) was developed, and the results of calculations using this method were compared with the results of an experimental study of such an injector. The jet of working steam coming out of a nozzle located at some distance from the cylindrical mixing chamber, at a sufficient temperature difference between steam and water, condenses in the injected water before entering the mixing chamber, raising the temperature of the injected water to tc and giving it a certain speed. This representation is in good agreement with published theoretical and experimental studies of the condensation of a steam jet in a space filled with liquid. When water enters the mixing chamber of a limited cross section, the water velocity increases, and its pressure decreases accordingly. If p is greater than the saturated vapor pressure at a certain temperature, then liquid moves in the mixing chamber and the process in the mixing chamber and diffuser is similar to the process in a water jet pump. In this case, an increase in pressure occurs in the mixing chamber due to the alignment of the velocity profile, which has a significant non-uniformity at the beginning of the mixing chamber. Then, in the diffuser, the water pressure rises to pc. In this case, regime or design factors have the same effect on the characteristics of the steam-water injector as on the characteristics of the water jet pump.

Significant differences occur at low injection coefficients. With a decrease in the flow rate of injected water and an unchanged C-fruit of the working steam, the water temperature rises to a value preceding the saturation temperature at pressure in the mixing chamber, and the injector fails due to a lack of water and condensation of all incoming working steam. This mode determines the minimum injection ratio.

With an increase in the injection ratio, when the flow rate of injected water increases as a result of a decrease in back pressure, the temperature of the water in the mixing chamber drops. At the same time, due to a change in the speed of the water in the mixing chamber, the pressure decreases.

With an increase in the flow rate of injected water to a certain limit, the pressure p in the inlet section of the mixing chamber decreases to saturation pressure at the temperature of the heated water t.

A decrease in backpressure does not lead to an increase in rapidity, and a further pressure drop in the mixing chamber is impossible and, therefore, the pressure drop, which determines the flow rate of injected water, cannot increase. The decrease in counterpressure in this case only leads to the boiling of water in the mixing chamber. This mode is similar to the cavitation mode of a water jet pump. The boiling of water in the mixing chamber thus determines the maximum (limiting) injection coefficient. It should be noted that this mode is the working one for nutrient injectors. It makes it possible to explain the independence of the injector performance from backpressure found from experiments when operating in the cavitation mode. Below is the derivation of the main calculation equations for a steam-water injector with the simplest cylindrical shape of the mixing chamber.

Characteristic equation. The momentum equation can be written as follows: /2 (GWpi + GKWM) - (Gp + + GH) Wi=fp + fin, where p is the vapor pressure in the outlet section of the working nozzle; Wpj - actual steam velocity in the outlet section of the nozzle; Wpj - steam velocity at adiabatic outflow; WHI is the velocity of the injected water in the annular section fn in the plane of the nozzle exit section; Y is the water velocity at the end of the mixing chamber. Let us make the following assumptions: 1) the section in the plane of the outlet section of the nozzle is so large that the velocity of the injected water in this section is close to zero and the momentum of the injected water GKWH, compared with the momentum of the working steam GWpi can be neglected; 2) the section of the receiving chamber in the plane the outlet section of the working nozzle significantly exceeds the section of the cylindrical mixing chamber.

The decrease in pressure from p1 to p2 occurs mainly at the end of the inlet section of the mixing chamber. When the outlet section of the nozzle is close to the value of the section of the mixing chamber, the pressure after the injector does not depend on the pressure of the injected water. The ratio of the sections has the same effect on the characteristics of the steam-water injector as on the characteristics of other types of jet devices: steam-jet compressors, water-jet pumps. An increase in the index leads to an increase in the injection coefficient and a decrease in water pressure after the injector p. As already noted, in a steam-water injector, the maximum and minimum injection coefficients are limited by the conditions of water boiling in the mixing chamber. The boiling of water in the mixing chamber will become lower than the saturation pressure (cavitation) at the temperature of the water in the mixing chamber t_. Both of these pressures (p, and p2) depend on the injection coefficient u for given parameters of the working steam and injected water and the dimensions of the injector. The water temperature in the mixing chamber is determined from the heat balance. At this temperature, the corresponding pv value is determined from the saturated steam tables. The water pressure at the beginning of the cylindrical mixing chamber p2 depends on the speed that the mass of injected water will receive before it enters the mixing chamber as a result of the exchange of impulses between the injected and working media.

If we assume that after the condensation of the working steam, a jet of the working fluid is formed, moving at a very high speed and, as a result, occupying a very small cross section, and also that the main exchange of momentum between this jet and the injected water occurs in a cylindrical mixing chamber, then the average velocity acquired by injected water at pressure p can be neglected. In this case, the water pressure at the beginning of the mixing chamber can be determined from the Bernoulli equation. A decrease in the pressure of the injected water at its constant temperature (t = const) leads to a reduction in the operating range of the injector, since the injection values ​​approach each other. An increase in the pressure of the working steam leads to a similar effect. At a constant pressure p and temperature t of the injected water, an increase in the pressure of the working steam p to a certain value leads to a breakdown in the operation of the injector. So, at UD = 1.8, the pressure of the injected water p = 80 kPa and its temperature / = 20 °C, the failure of the injector occurs when the pressure of the working steam increases to 0.96 MPa, and at / = 40 °C, the pressure of the working steam cannot be raised above 0.65 MPa. Thus, there are dependences of the limiting injection coefficients on the main geometrical parameter of the injector, as well as on operating conditions.

Achievable injection coefficients. In order to determine the achievable injection coefficient under the given operating conditions of the injector: the working steam parameters p and t, the parameters of the injected water, and the required water pressure after the injector, it is necessary to solve the characteristic equation and the equation of the limiting injection coefficient together. The position of the nozzle has a significant effect on the limiting injection coefficient: the smaller the distance of the nozzle from the mixing chamber, the lower the limiting injection coefficient. This can be explained by the fact that at small distances of the nozzle from the mixing chamber, the working steam does not have time to completely condense in the receiving chamber and occupies part of the inlet section of the mixing chamber, thereby reducing the cross section for the passage of water. As the distance of the nozzle from the mixing chamber increases, the limiting injection coefficient increases, but this increase gradually slows down. At the maximum distance of the nozzle from the mixing chamber (36 mm), the limiting injection coefficient is close to the calculated one. It can be assumed that its further increase will not lead to a noticeable increase in the limiting injection coefficient. The same regularity was observed at various pressures of the working steam and various diameters of the nozzle exit section. Based on the results obtained, all experiments with other mixing chambers and working nozzles were carried out at the maximum distance of the nozzle from the mixing chamber. Only at p = 0.8 MPa and an index of 1.8, the increase in the pressure of the injected water is less than p even, which is apparently explained by the fact that under these conditions the injector operation mode is close to stall. Indeed, at 1.8 and p = 0.8 MPa, the calculated minimum pressure of injected water is about 0.6 atm. At 1.8 and p = 0.8 MPa, the pressure of the injected water is close to the minimum. In this mode, the injector works with a limiting injection coefficient almost equal to the calculated one, but does not create the calculated pressure increase of the injected water. This phenomenon was also observed in other experiments when the injector operated in a regime close to stall. In order to realize theoretically possible increases in water pressure in the injector under these conditions, it is apparently necessary to make the flow part more careful, to choose the exact distance between the mixing chamber, etc. When calculating jet devices for pneumatic transport, the absolute pressure p is usually equal to 0 .1 MPa, unless an artificial vacuum is created in the receiving chamber of the apparatus. The value of pc, as a rule, is equal to the pressure loss in the network downstream of the apparatus. This pressure loss depends mainly on the pipe diameter downstream of the jet apparatus and the density of the transported medium. The same equations as for gas-jet injectors can be used to calculate the flow parameters in the characteristic sections of jet devices for pneumatic transport. With a supercritical degree of expansion of the working flow, the main dimensions of the working nozzle are calculated using the same formulas as for jet compressors. At a subcritical degree of expansion, the working nozzles have a conical shape, and the nozzle cross section is calculated. The flow rate through the nozzle at a subcritical degree of expansion is determined by the formulas, just as the axial size of the apparatus is determined.

Water-air ejectors. The device and features of the operation of a water-air ejector. In water-air ejectors, the working (ejecting) medium is water supplied under pressure to a converging nozzle, at the exit of which it acquires a high speed. The jet of water flowing from the nozzle into the receiving chamber carries with it the air or vapor-air mixture entering the chamber through the nozzle, after which the flow enters the mixing chamber and the diffuser, where the pressure increases. Along with the traditional shape of the flow path, water-air ejectors are used, in which the working fluid is supplied to the mixing chamber through several working nozzles or one nozzle with several holes (multi-jet nozzle).

As a result of an increase in the contact surface of the interacting media, such a nozzle, as shown by experimental studies, leads to a certain increase in the injection coefficient, all other things being equal.

Experimental studies have also shown the feasibility of increasing the length of the mixing chamber to 40-50 instead of 8-10 calibers for single-phase jet devices. This is apparently due to the fact that the formation of a homogeneous gas-liquid emulsion requires a greater length of the mixing path than the alignment of the velocity profile of a single-phase flow.

In a study specifically devoted to this issue, the authors show the process of destruction of the working jet as follows. The jet of the working fluid in the gas medium is destroyed as a result of the fact that drops fall out of the core of the jet. The destruction of the jet begins with the appearance of ripples (waves) on its surface at a distance of several diameters from the nozzle exit. Then the amplitude of the waves increases until drops or particles of liquid begin to fall into the environment. As the process develops, the core of the jet decreases and eventually disappears. The distance at which the jet breaks down is considered to be the mixing zone, in which the continuous medium is the injected gas. After an abrupt increase in pressure, a continuous medium becomes a liquid in which gas bubbles are distributed. The length of the mixing chamber must be sufficient to complete the mixing. If the mixing chamber is not long enough, the mixing zone passes into a diffuser, which reduces the efficiency of the water-air ejector.

For the range of the geometric parameter studied by the authors, the mixing length was 32–12 calibers of the mixing chamber, respectively. According to the research of the authors, the optimal form of the working nozzle is the diffusion of vacuum in various containers, etc. Water-air ejectors are always performed as single-stage. Designs of two-stage water-air ejectors or ejectors with a steam jet and a second water jet stage have been proposed, but they have not gained popularity. Under the conditions of condensing units, single-stage water-air ejectors compress the air contained in the steam-air mixture sucked from the condenser from a pressure of 2-6 kPa to atmospheric pressure or, if the water-air ejector is located at a certain height above the water level in the drain tank, to a pressure less than atmospheric by the value of the pressure of the water-air column mixtures in the drain pipe.

A characteristic feature of the working conditions of a water-air ejector is a large difference in the densities of the working water and the ejected air. The ratio of these values ​​can exceed 10. The mass injection coefficients of a water-air ejector are usually of the order of 10-6, and the volumetric injection coefficients are 0.2-3.0.

To conduct experimental studies, water-air ejectors are often made of a transparent material in order to be able to observe the nature of the movement of the medium. Experimental water-air ejectors VTI - with a measure of mixing with an inlet section made of plexiglass. Pressure is measured at four points along the length of the mixing chamber. Based on visual observations and pressure measurements along the length, the flow in the mixing chamber is represented as follows. The jet of water enters the mixing chamber, retaining its original cylindrical shape. Approximately at a distance of 2 calibers d3 from the beginning, the mixing chamber is already filled with a milky-white water-air emulsion (foam), and at the walls of the mixing chamber, reverse currents of the water-air emulsion are observed, which is again captured by the jet and entrained by it. This return movement is due to an increase in pressure along the length of the mixing chamber. For all considered modes, the pressure at the beginning of the mixing chamber is equal to p in the receiving chamber. At low counterpressures, the pressure increase in the cylindrical mixing chamber is relatively small. The main increase in pressure occurs in the diffuser. With an increase in counterpressure, this pattern changes: the pressure increase in the diffuser decreases, while in the mixing chamber it increases sharply, and it occurs abruptly in a relatively small section of the mixing chamber. The smaller the ratio of the cross section of the mixing chamber and the nozzle, the more pronounced the pressure jump. The place of the jump is clearly distinguishable, since it is not a milky-white emulsion that moves after it, but transparent water with air bubbles. The greater the ratio of the sections of the mixing chamber and the nozzle, the more developed the reverse currents of the water-air emulsion. With an increase in counterpressure, the pressure jump moves against the jet flow and, finally, at a certain counterpressure (p) reaches the beginning of the mixing chamber. In this case, the ejection of air by water stops, the entire mixing chamber is filled with clear water without air bubbles. Similar phenomena occur if the pressure of the working water decreases with a constant back pressure. For the calculation of the described types of jet apparatus, the use of the momentum equation proved to be very fruitful. This equation takes into account the main type of irreversible energy loss that occurs in jet devices - the so-called impact losses. The latter are determined mainly by the ratio of the masses and velocities of the injected and working medium. During the operation of a water-air ejector, the mass of injected air is thousands of times less than the mass of working water and therefore cannot change the speed of the working water jet to any extent.

The use in this case of the equation of impulses for interacting flows, as was done when deriving the calculation equations for single-phase apparatuses, leads to the values ​​of the achievable injection coefficient, which are several times higher than the experimental ones. Therefore, the methods for calculating water-air ejectors proposed so far by various authors are, in essence, empirical formulas that make it possible to obtain results that are more or less close to experimental data.

Experimental studies of water-air ejectors have shown that when the parameters of the ejector operation (pressure of the working, injected, compressed medium, mass air flow) change over a wide range, a fairly stable volumetric injection coefficient is maintained. Therefore, in a number of methods for calculating water-air ejectors, formulas are proposed for determining the volumetric injection coefficient. In the mixing chamber, due to the large contact surface between water and air, the air is saturated with water vapor. The temperature of the steam in the emulsion is almost equal to the temperature of the water. Therefore, the gas phase of the emulsion is a saturated vapor-air mixture. The total pressure of this mixture at the beginning of the mixing chamber is equal to the pressure of the injected dry air in the receiving chamber p. The partial pressure of air in the mixture is less than this pressure by the saturation vapor pressure at the temperature of the working medium. Since the air compressed in the ejector is part of the vapor-air mixture, then in the above expression for the volumetric injection coefficient, the value V is the volumetric flow rate of the vapor-air mixture, equal, according to Dalton's law, to the volumetric air flow rate at partial pressure p. The mass flow rate of the injected air can then be determined from the Clapeyron equation. When the pressure in the diffuser increases, the vapor contained in the emulsion condenses. Based on the test results of a water-air ejector with a single-jet nozzle and a cylindrical mixing chamber about 10 calibers long, it was proposed to use formulas for a water-jet pump to calculate the water-air ejector, in which the mass injection coefficient and is replaced by the volumetric one (the velocity of the ejected medium is zero), the specific volumes of the working compressed medium are the same.

Experiments show that as GB increases, the amount of vapor in the suction mixture at a given temperature decreases very quickly at first, and then more slowly. Accordingly, the characteristic pa -AGB) at / cm = const, starting on the y-axis at the point ra = pn (at GB = 0), increases and asymptotically approaches the characteristic corresponding to the suction of dry air at the same working water temperature tv. Thus, the characteristic of a water-jet ejector during the suction of a steam-air mixture of a given temperature differs significantly from the corresponding characteristic of a steam-jet ejector, which is (up to the overload point) a straight line, which corresponds to Gn = const.

For the sake of simplicity, it can be assumed with accuracy sufficient for practical purposes that the characteristic of a water-jet ejector when a steam-air mixture is sucked off at a given temperature consists of two sections, which, by analogy with the characteristic of a steam-jet ejector, can be called working and reloading. Within the working section of the characteristic of the water-jet ejector for With the indicated assumption, the overload section of the characteristic begins at the air flow rate G, which corresponds, in the case of dry air exhaustion, to a pressure pH equal to the pressure pp of saturated steam at the temperature of the exhausted mixture. For the reloading section, i.e., for the region GB > G, it can be assumed that the characteristic of the ejector when the vapor-air mixture is sucked out coincides with its characteristic in dry air at a given t.

When dry air is sucked off by a water-jet ejector, its productivity GH at a certain suction pressure p can be increased, or at a given G, the suction pressure can be reduced both by increasing the working water pressure pp and by reducing the back pressure, i.e., the pressure behind the diffuser pc. It is possible to reduce pc, for example, by installing a water jet ejector at a certain height above the water level in a drain tank or well. Due to this, the pressure after the diffuser is reduced by the value of the column pressure in the drain pipe. True, with the same working water pump, this will entail a slight decrease in water pressure in front of the working nozzle pp, but this will only partially reduce the positive effect achieved as a result of a decrease in pc. When installing a water jet ejector at a height H above the water level in the drain well, the pressure after diffuser will be Pc = P6 + Ap. When a water-jet ejector sucks off a steam-air mixture, a decrease in pc in the above way also favorably affects the characteristic of the ejector, but not so much due to a decrease in suction pressure within the working section of the characteristic, but due to an increase in the length of the working section of the characteristic (i.e., an increase in G).

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Ejection

ejection - and, pl. no, w. (fr. ejection ejection). those. 1. The process of mixing two different media (steam and water, water and sand, etc.), in which one medium, being under pressure, acts on the other and, dragging it along, pushes it out in the necessary ... ... Dictionary of foreign words of the Russian language

ejection - and, well. ejection f. ejection. 1. spec. The process of mixing what two media (steam and water, water and sand, etc.), in which one medium, being under pressure, acts on the other and, dragging it along, pushes it in the necessary direction. ... ... Historical Dictionary of Gallicisms of the Russian Language

ejection - Entrainment in a high-pressure, high-velocity flow of a low-pressure medium. The effect of ejection is that the flow with a higher ... ... Technical Translator's Handbook

ejection - ejection, and ... Russian spelling dictionary

ejection - (1 f), R., D., Pr. ezhe / ktsii ... Spelling Dictionary of the Russian Language

Ejection - the process of suction of a liquid or gas due to the kinetic energy of a jet of another liquid or gas ... Encyclopedic Dictionary of Metallurgy

ejection - 1. Nin. b. ike matdanen (par belen sunyn, su belen komnyn һ. b. sh.) kushylu processes; bu ochrakta ber matdә, basim astynda bulyp, ikenchesenә tәesir itә һәm, үzenә iyartep, any kirәkle yunәleshtә etep chygara 2. Tashu vakytynda turbinalarny normal ... ... Tatar teleneң anlatmaly үzlege

ejection - ezhek / qi / i [y / a] ... Morphemic-spelling dictionary

ejection - ejection ejection * Ejektion - the process of mixing two mediums (for example, gas and water), from which one, like a transit stream, perebuvayuchi under a vice, on a friend, p_dsmoktuє i vishtovhuє yogo at the singer directly. Transit stream becomes a worker ... Handy encyclopedic dictionary

small arms cartridge case reflection - Ndp cartridge case reflection. ejection of the cartridge case ejection of the cartridge case Removal of the cartridge case extracted from the chamber outside the small arms. [GOST 28653 90] Inadmissible, non-recommended ejection of the cartridge case ejection of the cartridge case Subjects small arms weapons Synonyms ... ... Technical Translator's Reference